Drive over the printing plate with a car....but I don't know if I would try it with a class of students....I saw the idea in one of the art magazines in the 70's

Soak the paper --blot it ...place it over the printing plate...put it in a sandwich of newsprint ---and cushion the whole thing with old towels (or felts if you have them)...drive over it a couple time (slowly)...and Voila! print.

Any other "old folks" out there on the list that remember reading about this method? Had to be sometime from 1976 to 1979.